The present invention relates to a drive system for an inverse kinematics device according to the preamble to claim 1.
Several inverse kinematics devices are known and as a rule go back to Paul Schatz (1898-1979), either directly as the inventor, or indirectly to him as the founder of inverse kinematics (see also: Paul Schatz, Rhymthmusforschung und Technik, Stuttgart 1975).
Such inverse kinematic devices have as a rule two parallel counter rotating axles, whose rotational angle ratio is       tan    ⁢          xe2x80x83        ⁢          ϕ      1        =            1      2        ⁢          xe2x80x83        ⁢    tan    ⁢          xe2x80x83        ⁢          ϕ      2      
and their unequal angular velocities conform to the equation             ω      1              ω      2        =      2    ⁢                  1        +                              1            4                    ⁢                      xe2x80x83                    ⁢                      tan            2                    ⁢                      xe2x80x83                    ⁢                      ϕ            1                                      1        +                              tan            2                    ⁢                      xe2x80x83                    ⁢                      ϕ            1                              
in so far as xcfx862 is replaced by xcfx861.
In the above relationships the reference direction is xcfx861=xcfx862=0 perpendicular to the connecting planes of the two axles; since the turning axles, as stated, turn in opposite directions, the positive rotation direction of xcfx861 is set against that of xcfx862.
Drives for such an inverse kinematic device are known, as for instance from CH 216 760 (D1), DE 1 145 455 (D2), DE 1 207 750 (D3), WO 80/01830 (D4), EP 0 176 749 (D5), SU 1 607 922 (D6), US 5 265 (D7), EP 0 584 301 (D8), EP 0 614 028 (D9).
These known devices represent several categories of solution: D1 and D2 are positive, geared drives, i.e. both the angular velocities xcfx861, xcfx862 and also the turning moments and power provided by the two axles are delivered by way of example by the drive, the correct angular relationships of xcfx861 and xcfx862 are prescribed by the drive, and no power exchange takes place between the two axles via the so-called middle member. This is, however, a purely mathematical concept: manufacturing and installation errors work themselves out in large loadings, above all on the various bearings.
D3 describes in principle a differential drive, which evens out the uneven running of the two parallel axles of the inverse kinematics device inherent in the construction. This is however at the price of a large power exchange via the quoted middle member, and on the other hand of a strong turning moment loading of the inverse kinematics device by the linking chain moved by the two axles.
D4 describes an energy store comprising a mass and spring element, D5 a hydraulic drive, D6 a similar drive with magnetic couplings, D8 finally a drive with two series coupled d.c. motors. This last named drive suffers, even if less obviously, from the same disadvantage as the solution with a differential drive, namely the loading on the inversion kinematic linking chain due to exchange turning moments. In D7 the drive comprises an induction motor, which provides only intermittent power, is expensive in manufacture and has a small efficiency. D8 finally describes a floating equalisation member connected between the two parallel axles, which on closer analysis however shows the same characteristics as the drives according to D1 and D2.
The aim of the present invention is the production of a drive for inverse kinematic devices, which has positive drive characteristics, but however avoids their disadvantages and is cost effective to manufacture. The aim is addressed in the characterising part of claim 1 with respect to its essential characteristics, in the claims dependent upon it with regard to further advantageous embodiments.